Research on and development of Software Defined Networking (SDN) is being advanced. SDN controls the behavior of the entire network using software. OpenFlow networks have been attracting attention as one of the technologies for achieving the SDN. The OpenFlow network is configured to include an OpenFlow controller (OF controller or OFC) and a plurality of OpenFlow switches (OF switch or OF-SW).
Each OpenFlow switch has a flow table. The flow table is configured to include one or more flow entries. In each flow entry, an operation for the corresponding flow is described. Specifically, each flow entry includes “matching condition”, “action”, and so on. The matching condition is equivalent to the identification information for identifying a flow to which a received packet belongs. The action describes the operation for the received packet in which the matching condition is met. Then, the OpenFlow switch searches the matching conditions in the flow table using the header information of the received packet and executes the corresponding action.
The OpenFlow controller manages the flow table of each OpenFlow switch. Also, the OpenFlow controller can update the contents of the flow table for each OpenFlow switch.
At the time of starting up the OpenFlow network, OpenFlow channels are established respectively between the OpenFlow controller and each OpenFlow switch. Then, messages are transmitted between the OpenFlow controller and each OpenFlow switch through the respective OpenFlow channels, and a flow table is configured for each OpenFlow switch. Thus, packet transfer can be achieved under the control of the OpenFlow controller. When the operation of the network is changed, the OpenFlow controller transmits a message that contains necessary information and an instruction to the corresponding OpenFlow switch through the OpenFlow channel. Then, the OpenFlow switch updates the flow table in response to the received message.
As described, each OpenFlow switch creates a flow table according to a message received from the OpenFlow controller through an OpenFlow channel and forwards a packet using the flow table. Thus, when a failure occurs in the OpenFlow channel that is established between the OpenFlow controller and the OpenFlow switch, the OpenFlow switch may not be able to forward the packet under the control of the OpenFlow controller. Therefore, a configuration or a method for recovering a failure of the OpenFlow channel has been proposed.
For example, a configuration duplicating the physical link between the OpenFlow controller and the OpenFlow switch is proposed. In this case, the OpenFlow channel is established on a work link. Then, when a failure occurs in the work link, an OpenFlow channel is established on a protection link.
A related art is described in WO2011/083785, Japanese Laid-open Patent Publication No. 2011-146982 (Japanese patent No. 5207082), Japanese Laid-open Patent Publication No. 2011-160363, Japanese Laid-open Patent Publication No. 2011-166384, Japanese Laid-open Patent Publication No. 2013-211706, Japanese Laid-open Patent Publication No. 2012-49674.
However, in the configuration where physical links between the OpenFlow controller and the OpenFlow switches are duplicated, the cost for establishing the network increases. Also, the number of physical ports provided for each OpenFlow switch increases.